R E S E A R C H Open AccessApplication of volumetric modulated arc therapy VMAT in a dual-vendor environment Barbara Dobler*, Karin Weidner, Oliver Koelbl Abstract Background and Purpose
Trang 1R E S E A R C H Open Access
Application of volumetric modulated arc therapy (VMAT) in a dual-vendor environment
Barbara Dobler*, Karin Weidner, Oliver Koelbl
Abstract
Background and Purpose: The purpose of this study was to assess plan quality and treatment time achievable with the new VMAT optimization tool implemented in the treatment planning system Oncentra MasterPlan® as compared to IMRT for Elekta SynergyS® linear accelerators
Materials and methods: VMAT was implemented on a SynergyS® linear accelerator (Elekta Ltd., Crawley, UK) with Mosaiq® record and verify system (IMPAC Medical Systems, Sunnyvale, CA) and the treatment planning system Oncentra MasterPlan® (Nucletron BV, Veenendaal, the Netherlands) VMAT planning was conducted for three typical target types of prostate cancer, hypopharynx/larynx cancer and vertebral metastases, and compared to standard IMRT with respect to plan quality, number of monitor units (MU), and treatment time
Results: For prostate cancer and vertebral metastases single arc VMAT led to similar plan quality as compared to IMRT For treatment of the hypopharynx/larynx cancer, a second arc was necessary to achieve sufficient plan
quality Treatment time was reduced in all cases to 35% to 43% as compared to IMRT Times required for
optimization and dose calculation, however, increased by a factor of 5.0 to 6.8
Conclusion: Similar or improved plan quality can be achieved with VMAT as compared to IMRT at reduced
treatment times but increased calculation times
Background
Volumetric modulated arc therapy (VMAT) allows
irra-diation with simultaneously varying dose rate, gantry
speed, collimator, and leaf positions It has been first
introduced by Otto in 2008 [1] and implemented for
Varian linear accelerators as RapidArc® [2-8] Various
treatment planning studies have been published,
com-paring RapidArc® and dynamic intensity modulated
radiation therapy (IMRT) or conventional stereotactic
treatments with regard to plan quality, delivery time,
and monitor units required per fraction dose
[2,3,7,9-19], using either in-house developed treatment
planning systems (TPS) or the Varian TPS Eclipse For
Elekta linear accelerators volumetric modulated arc
therapy became available under the label VMAT in
2008 The only commercially available treatment
plan-ning system was ERGO++ (3D Line Medical Systems/
Elekta Ltd, Crawley, UK), which, however, requires
initial definition of sub-arcs and manual adaptation of
the multileaf collimator (MLC) before automatic weight optimization and can therefore not be considered as a fully inverse planning system [20-23] Fully inverse treat-ment planning systems for Elekta linear accelerators have become commercially available only recently A few plan comparison studies have been published [24-26] using the treatment planning system Pinnacle (Philips Healthcare, Andover, MA) All of these studies showed similar plan quality at substantially reduced treatment times for VMAT as compared to IMRT In December 2009 a new VMAT optimization tool, imple-mented in Oncentra MasterPlan® v3.3, was released clinically, which allows VMAT optimization for Varian and Elekta linear accelerators with a linac-vendor inde-pendent planning system
The aim of this study was to investigate the feasibility
of VMAT with the new commercial combination of Oncentra MasterPlan® (Nucletron BV, Veenendaal, the Netherlands) and SynergyS® linear accelerators (Elekta Ltd, Crawley, United Kingdom) VMAT optimization was performed for typical target types usually treated with IMRT at our department and compared to standard
* Correspondence: barbara.dobler@klinik.uni-regensburg.de
Department of Radiotherapy, Regensburg University Medical Center, D-93042
Regensburg, Germany
© 2010 Dobler et al; licensee BioMed Central Ltd This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in
Trang 2IMRT with regard to plan quality, number of monitor
units, and treatment time Patients were selected for
whom treatment times required for IMRT are critical
due to possible intra-fractional organ movement or
patient discomfort and who therefore might benefit
sub-stantially from the advancement from IMRT to VMAT
Methods
Linear accelerator and record and verify system
A SynergyS® linear accelerator with 6MV photons,
equipped with a BeamModulator™ head, an iViewGT™
electronic portal imaging device, and an on-board
cone-beam CT XVI is used for VMAT delivery The
Beam-Modulator™ head has a multileaf collimator which
consists of 40 leaf pairs of 4 mm width at isocenter and
allows unrestricted leaf interdigitation Fixed diaphragms
limit the maximum field size of 21 cm × 16 cm, and
there are no moveable jaws Minimum and maximum
number of MU per degree of gantry rotation are 0.10
MU/° and 20.0 MU/° respectively, minimum MU per
cm leaf travel is 0.30 MU/cm, maximum gantry speed is
6.00 °/s Maximum leaf speed is 2.4 cm/s, the dynamic
minimum leaf gap 0.14 cm, and the static minimum leaf
gap 0.0 cm The maximum nominal dose rate is 500
MU/min Seven fixed dose rate levels are available, each
half the dose rate of the next higher level, continuous
variation is not possible Actual dose rates may differ
from nominal dose rates by ±25% During VMAT
deliv-ery the fastest combination of dose rate, gantry speed
and leaf speed is automatically selected by the linac
con-trol system Precise Desktop® 7
Treatment planning system
Treatment planning is performed with Oncentra
MasterPlan® v3.3 SP1, released clinically in December
2009, on a 64 bit Windows system with 8 GB RAM and
8-core processor For beam data modeling the above
mentioned VMAT specific parameters of the linac have
to be defined Since the TPS only allows for 5 different
dose rates, two dose rates had to be omitted We kept
the 5 higher and omitted the two lower dose rates,
because according to the literature the main advantage
of VMAT as compared to IMRT is the short treatment
time, which would be prolonged if higher dose rates
would be omitted This is also in concordance with
Bed-ford’s recommendation not to use dose rates below 75
MU/min to a large extent due to instabilities of the
linac below 37 MU/min [27] Since the linac
automati-cally selects the fastest combination of gantry speed, leaf
speed and dose rate, these parameters are only used to
ensure compliance with machine constraints and
esti-mate treatment time in the optimization They are,
how-ever, not transferred to the linac and have therefore no
influence on the delivery
For treatment planning, beams are set up in the Beam Modeling module (BM), in which the treatment unit, energy and collimator angle are defined by the user Gantry speed, leaf positions and dose rate are subject to optimization, the collimator angle, however, is kept con-stant at the predefined value for each arc Other user defined parameters for the optimization include start gantry angle, rotation direction, arc length, gantry angle spacing between subsequent control points (2° to 6°), maximum delivery time, number of arcs, and con-strained leaf motion in cm/°
Optimization is performed in the Optimization Mod-ule, which allows the user to choose between the IMRT options “Intensity Modulation” (IM) with subsequent leaf sequencing, and the direct machine parameter opti-mization“Direct Step and Shoot” (DSS), and VMAT
In DSS a fluence optimization with subsequent leaf sequencing is performed for static fields for a few itera-tions to get an initial guess for the segments In the next step, the gradients of the objective function are cal-culated with respect to leaf positions and weights, allow-ing direct optimization of deliverable MLC segments, which leads to improved results as compared to IM [28-30]
VMAT optimization starts with a fluence optimization for gantry angle spacing of 24° and subsequent MLC sequencing, generating 2 segments per gantry angle The segments are then spread out evenly and cloned to achieve the required gantry angle spacing as defined by the user Based on this starting point a direct machine parameter optimization is performed, taking machine restrictions into account, followed by a final accurate dose calculation and segment weight optimization The method is a successor of and very similar to the method described in [31], where new segments are created by linear interpolation instead of cloning
Continuous delivery is discretized and approximated
by the calculation of static beams separated by 2° to 6°, depending on the user defined gantry angle spacing The result of the accurate dose calculation is used as starting point for an automatic second optimization run
to improve results [32] For more than one arc, the dual arc option is available, which groups the segments, such that the required leaf movement is reduced, i.e one arc contains segments with leaves positioned more to the left, and the other more to the right Detailed informa-tion about the optimizer has been published in [31] Commissioning of the system combination of Oncen-tra MasterPlan®, Mosaiq® and SynergyS® for VMAT has been successfully completed with individual plan verifi-cations within 3% dose tolerance and 3 mm distance to agreement Validation has been performed by absolute 2D-dosimetry using the 2D-array MatriXXEvolution® (IBA Dosimetry, Schwarzenbruck, Germany) A description of
Trang 3the commissioning procedure and detailed results,
how-ever, is beyond the scope of this study and will be
pub-lished separately
Treatment planning feasibility study
For a selection of patients who had undergone or were
currently under IMRT treatment at our department,
VMAT plans were optimized and compared to the
IMRT plans to assess plan quality achievable with
VMAT The feasibility study was performed on three
patients with typical target geometries of head and neck
and prostate cancer, as well as spinal cord sparing
irra-diation of vertebrae
1 A 64 year old patient with prostate cancer, pT3b,
pN0, cM0, R1, with a planning target volume (PTV)
of 424.1 cm3 and a boost volume of 241.7 cm3 The
PTV covered the prostatic fossa and the region of
seminal vesicles defined by pelvic CT with 8 mm
margin for setup, organ motion and delineation
uncertainties Dose prescription was 60 Gy in 2 Gy
fractions to the average of the PTV, and 70 Gy in 2
Gy fractions to the boost volume The bladder,
rec-tum and the femoral heads were delineated as organs
at risk (OAR) The volumes of rectum and bladder,
which were not overlapping with the PTV that was
extended by an additional 0.8 cm margin, were used
as help structures for optimization and evaluation of
plan quality, referred to as“rectum - PTV” and
“blad-der - PTV” respectively The feasibility study was
per-formed for the first series only Dose volume
objectives (DVO) based on dose prescription and
OAR tolerance doses are listed in table 1
2 A 52 year old male patient with cancer of the
hypo-pharynx/larynx T4, N2c, M0, with 626.2 cm3PTV,
and 452.2 cm3 boost volume The definition of PTV
and organs at risk was according to literature [33]
Dose prescription was 60 Gy in 2 Gy fractions to the
average of the PTV, and 70 Gy in 2 Gy fractions to
the average of the boost volume The spinal cord, the
brain stem, the parotids, the temporomandibular joint,
the lung, and the lenses were delineated as OAR The
feasibility study was performed for the PTV only Dose
volume objectives based on dose prescription and
OAR tolerance doses are listed in table 2
3 A 70 year old female patient with metastases in
the lumbar vertebra, with a volume of 342.8 cm3 of
the PTV and 60.7 cm3 of the GTV The PTV was
defined as the whole vertebral body with a 5 mm
margin, the definition of GTV based on tumour
mass identified by nuclear magnetic resonance
tomography Dose prescription was 44 Gy to the
average of the PTV in fractions of 2.0 Gy and 55 Gy
to the average of the GTV volume in fractions of 2.5
Gy, treated as simultaneous integrated boost (SIB) The spinal cord and the kidneys were delineated as OAR Dose volume objectives based on dose
Table 1 Treatment plan comparison for prostate cancer
Structure Parameter DVO Single arc IMRT PTV D 50% Uniform 60.0 Gy 59.9 Gy
H Dose 5.5 7.0
V 95% 60 Gy 99.9% 97.2% Normal Tissue D 1% ≤ 60.0 Gy 60.0 Gy 59.9 Gy
D 10% ≤ 30.0 Gy 29.9 Gy 31.7 Gy
D 25% ≤ 15.0 Gy 17.5 Gy 17.7 Gy Rectum D 1% - 60.7 Gy 60.2 Gy Rectum - PTV D 1% ≤ 40.0 Gy 37.8 Gy 38.5 Gy Bladder D 1% - 61.5 Gy 62.2 Gy Bladder - PTV D 1% ≤ 30.0 Gy 47.4 Gy 47.4 Gy Left Femoral Head D 50% - 28.5 Gy 29.9 Gy Right Femoral Head D 50% - 29.8 Gy 28.9 Gy Monitor Units MU/2.0 Gy - 695 687 Time Calculation - 16:30 min 2:52 min
Delivery - 4:45 min 11:00 min
D X% is the dose delivered to X% of the volume in Gy, V 95% the volume receiving 95% of the prescription dose in%, Homogeneity H = (D 5% - D 95% )/
D average
Table 2 Treatment plan comparison cancer for hypopharynx/larynx
Structure Parameter DVO Dual Arc Single
Arc
IMRT PTV D 50% Uniform 60.0 Gy 60.5 Gy 59.7 Gy
H Dose 7.0 9.4 8.0
V 95% 60 Gy 97.8% 95.4% 95.7% Normal
Tissue
D 1% ≤ 60 Gy 58.4 Gy 58.1 Gy 57.8 Gy
D 20% ≤ 21 Gy 20.1 Gy 20.4 Gy 21.5 Gy
D 60% ≤ 4 Gy 1.9 Gy 1.9 Gy 2.0 Gy Left Parotid D 50% ≤ 26 Gy 23.7 Gy 23.1 Gy 29.4 Gy Right Parotid D 50% ≤ 26 Gy 20.6 Gy 23.3 Gy 26.4 Gy Spinal Cord D 1 ccm ≤ 39 Gy 36.9 Gy 39.8 Gy 37.6 Gy Brain Stem D 1 ccm ≤ 43 Gy 34.4 Gy 41.5 Gy 36.9 Gy Left Joint* D 50% - 2.6 Gy 2.7 Gy 2.9 Gy Right Joint* D 50% - 2.3 Gy 2.2 Gy 2.5 Gy Monitor
Units
MU/2.0 Gy - 715 552 799 Time Calculation - 33:10
min 16:30 min 4:52 min Delivery - 5:00 min 2:08 min 14:15
min
*temporomandibular joint
D X% and D 1 ccm are the doses delivered to X% of the volume and 1 cm 3 respectively, V 95% the volume receiving 95% of the prescription dose in%,
Trang 4prescription and OAR tolerance doses are listed in
table 3
For all patients the normal tissue was defined as an
OAR by subtracting the PTV from the patient outline
and used during optimization to prevent high dose areas
outside the PTV
Several planning studies have been published
compar-ing fluence modulation with subsequent leaf sequenccompar-ing
IM and the direct aperture optimization DSS in
Oncen-tra MasterPlan®, showing clear advantage for DSS
[28-30] Therefore, the reference IMRT plans were
opti-mized with DSS in this study Seven equispaced beams
have been used in all IMRT plans
For the optimization of VMAT plans, single arcs ranging
from 182° to 178° gantry angle with a gantry angle spacing
of 4° and the leaf motion constrained to 0.5 cm/° were
used The collimator angle was set to 45° as suggested in
[34], except for the head and neck case for which the
colli-mator had to be set to 0° to ensure PTV coverage
Maxi-mum delivery time was set to 150 s per arc for patient
number 1 and 2, and to 200 s per arc for patient number
3 If the plan quality achievable with single arc was not
comparable to IMRT, plans were re-optimized using the
dual arc option leaving gantry angle range and spacing
unchanged Dose volume objectives were kept identical to
the IMRT plans In addition to plan quality the times
required for planning and irradiation were compared
Cal-culation times were measured from the start of the
optimi-zation until the end of the final dose calculation,
irradiation times were measured from the start of the first
beam until the end of the last beam
Results
The feasibility study showed similar plan quality at reduced delivery times and similar number of MU per fraction for VMAT as compared to IMRT in all cases:
1 For the prostate case, single arc VMAT showed better dose homogeneity and target coverage, and similar, mostly even lower dose to the organs at risk Time for optimization and dose calculation increased by a factor of 5.8, treatment time was reduced to 43% Detailed information is given in table 1 Figure 1 shows the dose distribution in transversal CT-slices, figure 2 the respective dose volume histograms (DVH)
2 For the case with cancer of the hypopharynx/larynx, single arc VMAT showed similar target coverage and better sparing of the parotids, but deteriorated homo-geneity as compared to IMRT Better overall plan quality including target coverage, homogeneity inside the PTV, as well as OAR sparing could be achieved with dual arc VMAT Even the relative volume of the normal tissue, receiving doses between 20.0 Gy and 50.0 Gy is smaller in case of the dual arc treatment Only the relative volume of the normal tissue receiving between 5.0 Gy and 20.0 Gy is slightly larger Detailed information is given in table 2 Figure 3 shows the dose distribution for dual arc as compared to IMRT in transversal slices, figure 4 the respective DVH Seg-ment shapes for a selected gantry angle are shown in figure 5, illustrating the grouping of the segments into arcs with respect to the leaf positions For dual arc, time for optimization and dose calculation increased
by a factor of 6.8, treatment time was reduced to 35%,
as compared to IMRT
3 For the patient with metastases in the lumbar ver-tebra, single arc VMAT showed similar plan quality
as compared to IMRT Doses to the GTV were simi-lar, median dose and D95%for the PTV higher, doses
to the kidney were also higher but still below the tolerance and fulfilling the DVO used in optimiza-tion Time for optimization and dose calculation increased by a factor of 5.0, treatment time was reduced to 41% Since patients with bone metastases suffer from pain and are not able to keep the posi-tion for a long time, the VMAT plan was considered superior because of the reduced treatment time Detailed information is given in table 3 Figure 6 shows the dose distribution in transversal, sagittal and coronal slices, figure 7 the respective DVH Patient 1 and 3 have actually been treated with VMAT after successful completion of commissioning, patient 2 had already finished treatment
Table 3 Treatment plan comparison for metastases of the
lumbar vertebra (SIB)
Structure Parameter DVO Single Arc IMRT
GTV D 50% Uniform 55.0 Gy 55.0 Gy
H Dose 7.3 7.1 GTV V 95% 55 Gy 95.6% 95.9%
PTV D 95% ≥ 40.0 Gy 41.4 Gy 40.5 Gy
Normal Tissue D 1% ≤ 40.0 Gy 41.3 Gy 42.6 Gy
D 20% ≤ 15.0 Gy 13.6 Gy 8.0 Gy
D 60% ≤ 5.0 Gy 1.8 Gy 1.3 Gy Left Kidney D 40% ≤ 10.0 Gy 9.4 Gy 7.8 Gy
Right Kidney D 40% ≤ 10.0 Gy 9.0 Gy 5.3 Gy
Spinal Cord D 1 ccm ≤ 45.0 Gy 41.7 Gy 41.1 Gy
Monitor Units MU/2.5 Gy - 698 736
Time Calculation - 13:50 min 2:45 min
Delivery - 4:30 min 11:00 min
D X% and D 1 ccm are the doses delivered to X% of the volume and 1 cm 3
respectively, V 95% the volume receiving 95% of the prescription dose in%,
Homogeneity H = (D 5% - D 95% )/D average
Trang 5The VMAT optimization tool implemented in Oncentra
MasterPlan® v.3.3 allows creating VMAT plans with
similar or better plan quality as compared to IMRT
which can be delivered in substantially reduced
treat-ment time on an Elekta SynergyS® linear accelerator For
the treatment of prostate cancer and vertebral
metastases, the required plan quality could be achieved with one single arc VMAT, which is in agreement with the results published for other types of equipment [4,18,24,35] For the treatment of hypopharynx/larynx cancer, however, single arc VMAT did not lead to suffi-cient plan quality, reducing target homogeneity as com-pared to IMRT and violating the DVO for the spinal
Figure 1 Dose distributions for prostate cancer Comparison of dose distributions achieved with 7-field IMRT (left) and Single Arc VMAT (right) on representative transversal (top) and sagittal (bottom) CT slices The PTV is drawn in red, the bladder in orange, the rectum in maroon, and the femoral heads in green Isodose lines are shown in percent of the prescription dose, i.e 60 Gy to the average of the PTV.
Figure 2 Dose volume histograms for prostate cancer Comparison of dose volume histograms achieved with 7-field IMRT (dotted lines) and Single Arc VMAT (solid lines) Plan quality is slightly better for VMAT, with better target coverage and homogeneity and lower OAR doses.
Trang 6Figure 3 Dose distributions for hypopharynx/larynx cancer Comparison of dose distributions achieved with 7-field IMRT (left) and Dual Arc VMAT (right) on representative transversal (top) and sagittal (bottom) CT slices The PTV is drawn in red, the parotids in blue and purple, the spinal cord in green, and the brain stem in bright blue Isodose lines are shown in percent of the prescription dose, i.e 60 Gy to the average of the PTV.
Trang 7cord The dual arc technique strongly improved plan
quality as compared to single arc VMAT but also to
IMRT, which also complies with publications to other
VMAT solutions [14,24,36] The findings of Bertelsen
[25], who reported good results for single arc VMAT
for head and neck cancer using SmartArc® (Philips
Healthcare, Andover, MA) could not be confirmed In
this case, however, plan comparison was performed for
simultaneous treatment of three target levels, which
requires certain dose heterogeneity inside the target
The applicability of the system to simultaneous
inte-grated boost concepts has been demonstrated for the
treatment of vertebral metastases In this case, a single arc
was sufficient to achieve the required plan quality The same concept can be applied for SIB treatments of other target types like prostate or head and neck cancers It might even be possible that single arc treatments are in general suitable for SIB concepts due to the required dose heterogeneity inside the target, which would also explain the results of Bertelsen [25] mentioned above This, how-ever, remains to be investigated in a separate study
In the VMAT solution implemented in Oncentra MasterPlan® v3.3, segment shapes and weights are sub-ject to optimization, which is one of the main differ-ences to the treatment planning system ERGO++®: In ERGO++® segment shapes have to be defined by the
Figure 4 Dose volume histograms for hypopharynx/larynx cancer Comparison of dose volume histograms achieved with 7-field IMRT (dotted lines) and Dual Arc VMAT (solid lines) Plan quality is slightly better for VMAT, with somewhat lower dose to the parotids.
Figure 5 Typical MLC positions resulting from Dual Arc optimization In Dual Arc VMAT, segments are grouped into arcs such that leaf travel is minimized during each rotation In the example shown in this figure, arc 1 contains segments with leaves positioned more to the left, arc 2 to the right of the field.
Trang 8user prior to optimization, and only the segment
weights are optimized
The quality of the VMAT plans resulting from
optimi-zation in ERGO++® is therefore highly dependent on the
individual user’s experience in creating suitable segment
shapes The VMAT solution implemented in Oncentra
MasterPlan® v3.3 in contrary does not require any user
input for the segment shapes Segment shapes and weights are resulting from the optimization process and the resulting plan quality is therefore less dependent on the individual user
The number of monitor units per fraction in this study was similar for VMAT and IMRT, a significant reduction as reported for Varian linacs could not be
Figure 6 Dose distributions for metastases in the lumbar vertebra Comparison of dose distributions achieved with 7-field IMRT (left) and Single Arc VMAT (right) on representative transversal (top) and sagittal (bottom) CT slices The PTV is drawn in red, the GTV in orange, the spinal cord in green, and the kidneys in maroon Isodose lines are shown in percent of the prescription dose, i.e 55 Gy to the average of the GTV.
Figure 7 Dose volume histograms for metastases in the lumbar vertebra Comparison of dose volume histograms achieved with 7-field IMRT (dotted lines) and Single Arc VMAT (solid lines) Using the same dose volume objectives for optimization, higher doses to the PTV are achieved with VMAT for almost identical GTV coverage and homogeneity and sparing of the spinal cord but somewhat higher dose to the kidneys.
Trang 9observed [36], since the values found for IMRT were
already considerably lower than the ones reported for
Varian Treatment times, however, could be substantially
reduced to 35% to 43% as compared to IMRT, whereas
calculation times were 5.0 to 6.8 times higher for
VMAT
The combination of plan quality and treatment time
shows clear advantage of VMAT over IMRT: Treatment
time is a crucial factor especially for patients who suffer
from pain or are not able to keep a certain position for
a longer time, as it is the case e.g for patients with
bone metastases, or for patients with significant internal
organ movement, e.g patients with prostate cancer, for
which the actual delivered dose distribution might differ
significantly from the planned dose distribution due to
intra-fractional movement In these cases even a single
arc leads to the required plan quality, allowing reducing
overall treatment time from 11 minutes to well below 5
minutes For the patient with hypopharynx/larynx
can-cer the dual arc VMAT showed better plan quality at
only 33% of the treatment time, which reduces patient
discomfort in the rigid mask system The reduction in
delivery time leads to better patient comfort and
possi-bly also quality of delivery, and simultaneously reduces
the workload and increases availability of the linac
The only drawback found for VMAT as compared to
IMRT was the increased calculation time This, however,
has no impact on patient treatment or on the workload
but is only affecting availability of the treatment
plan-ning station Workload for the planner is virtually the
same for VMAT as for IMRT, since the steps of the
planning procedure, which require user interaction, like
definition of structures, beam setup, definition of DVO,
are the same in both cases In the future calculation
times may be reduced using a processor with more than
8 cores or performing the dose calculation on the GPU
processor, as it will be implemented in the next version
of Oncentra MasterPlan®
It could be shown that VMAT planning with
Oncen-tra MasterPlan® has the potential to produce better plan
quality requiring less delivery time as compared to
IMRT However, dedicated planning studies should be
performed, varying the user definable parameters e.g
maximum treatment time, number of arcs, and gantry
angle range, to identify the best parameter set to achieve
optimal combination of plan quality and treatment time
for each target type
Conclusion
Oncentra MasterPlan® allows achieving comparable or
superior plan quality with VMAT as compared to
IMRT Times required for optimization and dose
calcu-lation are increased, the number of monitor units per
fraction is similar, and treatment times are strongly reduced
Abbreviations CT: Computed Tomography; DSS: Direct Step and Shoot optimization; DVH: Dose Volume Histogram; DVO: Dose Volume Objective; GTV: Gross Tumour Volume; IM: Intensity Modulation with subsequent sequencing; IMRT: Intensity Modulated Radiation Therapy; MLC: Multi-Leaf Collimator; MU: Monitor Units; OAR: Organ at Risk; PTV: Planning Target Volume; SIB: Simultaneous Integrated Boost; TPS: Treatment Planning System; VMAT: Volumetric Modulated Radiation Therapy
Acknowledgements The authors would like to thank David Robinson (Nucletron, Columbia, MD) and Markus Rankl (Theranostic, Solingen, Germany) for valuable discussions Authors ’ contributions
BD conceived of and designed the study, performed treatment planning and plan comparison and drafted the manuscript KW performed part of the treatment planning OK helped to draft the manuscript All authors read and approved the final manuscript.
Competing interests This work was partly supported by Theranostic.
Received: 12 August 2010 Accepted: 25 October 2010 Published: 25 October 2010
References
1 Otto K: Volumetric modulated arc therapy: IMRT in a single gantry arc Med Phys 2008, 35(1):310-317.
2 Cozzi L, Dinshaw KA, Shrivastava SK, Mahantshetty U, Engineer R, Deshpande DD, Jamema SV, Vanetti E, Clivio A, Nicolini G, et al: A treatment planning study comparing volumetric arc modulation with RapidArc and fixed field IMRT for cervix uteri radiotherapy Radiother Oncol 2008, 89(2):180-191.
3 Fogliata A, Yartsev S, Nicolini G, Clivio A, Vanetti E, Wyttenbach R, Bauman G, Cozzi L: On the performances of Intensity Modulated Protons, RapidArc and Helical Tomotherapy for selected paediatric cases Radiat Oncol 2009, 4:2.
4 Kjaer-Kristoffersen F, Ohlhues L, Medin J, Korreman S: RapidArc volumetric modulated therapy planning for prostate cancer patients Acta Oncol
2009, 48(2):227-232.
5 Korreman S, Medin J, Kjaer-Kristoffersen F: Dosimetric verification of RapidArc treatment delivery Acta Oncol 2009, 48(2):185-191.
6 Ling CC, Zhang P, Archambault Y, Bocanek J, Tang G, Losasso T:
Commissioning and quality assurance of RapidArc radiotherapy delivery system Int J Radiat Oncol Biol Phys 2008, 72(2):575-581.
7 Oliver M, Ansbacher W, Beckham WA: Comparing planning time, delivery time and plan quality for IMRT, RapidArc and Tomotherapy J Appl Clin Med Phys 2009, 10(4):3068.
8 Weber DC, Wang H, Cozzi L, Dipasquale G, Khan HG, Ratib O, Rouzaud M, Vees H, Zaidi H, Miralbell R: RapidArc, intensity modulated photon and proton techniques for recurrent prostate cancer in previously irradiated patients: a treatment planning comparison study Radiat Oncol 2009, 4:34.
9 Lagerwaard FJ, van der Hoorn EA, Verbakel WF, Haasbeek CJ, Slotman BJ, Senan S: Whole-brain radiotherapy with simultaneous integrated boost
to multiple brain metastases using volumetric modulated arc therapy Int J Radiat Oncol Biol Phys 2009, 75(1):253-259.
10 Lagerwaard FJ, Meijer OW, van der Hoorn EA, Verbakel WF, Slotman BJ, Senan S: Volumetric modulated arc radiotherapy for vestibular schwannomas Int J Radiat Oncol Biol Phys 2009, 74(2):610-615.
11 Nicolini G, Clivio A, Fogliata A, Vanetti E, Cozzi L: Simultaneous integrated boost radiotherapy for bilateral breast: a treatment planning and dosimetric comparison for volumetric modulated arc and fixed field intensity modulated therapy Radiat Oncol 2009, 4:27.
12 Fogliata A, Clivio A, Nicolini G, Vanetti E, Cozzi L: Intensity modulation with photons for benign intracranial tumours: a planning comparison of
Trang 10volumetric single arc, helical arc and fixed gantry techniques Radiother
Oncol 2008, 89(3):254-262.
13 Clivio A, Fogliata A, Franzetti-Pellanda A, Nicolini G, Vanetti E, Wyttenbach R,
Cozzi L: Volumetric-modulated arc radiotherapy for carcinomas of the
anal canal: A treatment planning comparison with fixed field IMRT.
Radiother Oncol 2009, 92(1):118-124.
14 Vanetti E, Clivio A, Nicolini G, Fogliata A, Ghosh-Laskar S, Agarwal JP,
Upreti RR, Budrukkar A, Murthy V, Deshpande DD, et al: Volumetric
modulated arc radiotherapy for carcinomas of the oro-pharynx,
hypo-pharynx and larynx: a treatment planning comparison with fixed field
IMRT Radiother Oncol 2009, 92(1):111-117.
15 Shaffer R, Nichol AM, Vollans E, Fong M, Nakano S, Moiseenko V,
Schmuland M, Ma R, McKenzie M, Otto K: A Comparison of Volumetric
Modulated Arc Therapy and Conventional Intensity-Modulated
Radiotherapy for Frontal and Temporal High-Grade Gliomas Int J Radiat
Oncol Biol Phys 2010, 76(4):1177-1184.
16 Shaffer R, Morris WJ, Moiseenko V, Welsh M, Crumley C, Nakano S,
Schmuland M, Pickles T, Otto K: Volumetric modulated Arc therapy and
conventional intensity-modulated radiotherapy for simultaneous
maximal intraprostatic boost: a planning comparison study Clin Oncol (R
Coll Radiol) 2009, 21(5):401-407.
17 Popescu CC, Olivotto IA, Beckham WA, Ansbacher W, Zavgorodni S,
Shaffer R, Wai ES, Otto K: Volumetric Modulated Arc Therapy Improves
Dosimetry and Reduces Treatment Time Compared To Conventional
Intensity-Modulated Radiotherapy for Locoregional Radiotherapy of
Left-Sided Breast Cancer and Internal Mammary Nodes Int J Radiat Oncol Biol
Phys 2010, 76(1):287-295.
18 Palma D, Vollans E, James K, Nakano S, Moiseenko V, Shaffer R, McKenzie M,
Morris J, Otto K: Volumetric modulated arc therapy for delivery of
prostate radiotherapy: comparison with intensity-modulated
radiotherapy and three-dimensional conformal radiotherapy Int J Radiat
Oncol Biol Phys 2008, 72(4):996-1001.
19 Clark GM, Popple RA, Young PE, Fiveash JB: Feasibility of Single-Isocenter
Volumetric Modulated Arc Radiosurgery for Treatment of Multiple Brain
Metastases Int J Radiat Oncol Biol Phys 2010, 76(1):296-302.
20 Haga A, Nakagawa K, Shiraishi K, Itoh S, Terahara A, Yamashita H,
Ohtomo K, Saegusa S, Imae T, Yoda K, et al: Quality assurance of
volumetric modulated arc therapy using Elekta Synergy Acta Oncol 2009,
48(8):1193-1197[http://informahealthcare.com/doi/pdf/10.3109/
02841860903081905].
21 Wolff D, Stieler F, Hermann B, Heim K, Clausen S, Fleckenstein J, Polednik M,
Steil V, Wenz F, Lohr F: Clinical Implementation of Volumetric
Intensity-Modulated Arc Therapy (VMAT) with ERGO++ Strahlenther Onkol 2010,
186(5):280-288.
22 Wolff D, Stieler F, Welzel G, Lorenz F, Abo-Madyan Y, Mai S, Herskind C,
Polednik M, Steil V, Wenz F, et al: Volumetric modulated arc therapy
(VMAT) vs serial tomotherapy, step-and-shoot IMRT and 3D-conformal
RT for treatment of prostate cancer Radiother Oncol 2009, 93(2):226-233.
23 Stieler F, Wolff D, Lohr F, Steil V, Abo-Madyan Y, Lorenz F, Wenz F, Mai S: A
fast radiotherapy paradigm for anal cancer with volumetric modulated
arc therapy (VMAT) Radiat Oncol 2009, 4:48.
24 Guckenberger M, Richter A, Krieger T, Wilbert J, Baier K, Flentje M: Is a
single arc sufficient in volumetric-modulated arc therapy (VMAT) for
complex-shaped target volumes? Radiother Oncol 2009, 93(2):259-265.
25 Bertelsen A, Hansen CR, Johansen J, Brink C: Single Arc Volumetric
Modulated Arc Therapy of head and neck cancer Radiother Oncol 2010.
26 Matuszak MM, Yan D, Grills I, Martinez A: Clinical Applications of
Volumetric Modulated Arc Therapy Int J Radiat Oncol Biol Phys 2010.
27 Bedford JL, Warrington AP: Commissioning of volumetric modulated arc
therapy (VMAT) Int J Radiat Oncol Biol Phys 2009, 73(2):537-545.
28 Dobler B, Pohl F, Bogner L, Koelbl O: Comparison of direct machine
parameter optimization versus fluence optimization with sequential
sequencing in IMRT of hypopharyngeal carcinoma Radiat Oncol 2007,
2:33.
29 Dobler B, Koelbl O, Bogner L, Pohl F: Direct machine parameter
optimization for intensity modulated radiation therapy (IMRT) of
oropharyngeal cancer –a planning study J Appl Clin Med Phys 2009,
10(4):3066.
30 Treutwein M, Hipp M, Kolbl O, Bogner L: IMRT of prostate cancer: a
comparison of fluence optimization with sequential segmentation and
direct step-and-shoot optimization Strahlenther Onkol 2009, 185(6):379-383.
31 Bzdusek K, Friberger H, Eriksson K, Hardemark B, Robinson D, Kaus M: Development and evaluation of an efficient approach to volumetric arc therapy planning Med Phys 2009, 36(6):2328-2339.
32 Zhang P, Yang J, Hunt M, Mageras G: Dose correction strategy for the optimization of volumetric modulated arc therapy Med Phys 2010, 37(6):2441-2444.
33 Budach V, Stuschke M, Budach W, Baumann M, Geismar D, Grabenbauer G, Lammert I, Jahnke K, Stueben G, Herrmann T, et al: Hyperfractionated accelerated chemoradiation with concurrent fluorouracil-mitomycin is more effective than dose-escalated hyperfractionated accelerated radiation therapy alone in locally advanced head and neck cancer: final results of the radiotherapy cooperative clinical trials group of the German Cancer Society 95-06 Prospective Randomized Trial J Clin Oncol
2005, 23(6):1125-1135.
34 Verbakel WF, Senan S, Lagerwaard FJ, Cuijpers JP, Slotman BJ: Comments
on ‘Single-Arc IMRT?’ Phys Med Biol 2009, 54(8):L31-34, author reply L35-36.
35 Zhang P, Happersett L, Hunt M, Jackson A, Zelefsky M, Mageras G: Volumetric Modulated Arc Therapy: Planning and Evaluation for Prostate Cancer Cases Int J Radiat Oncol Biol Phys 2010, 76(5):1456-1462.
36 Verbakel WF, Cuijpers JP, Hoffmans D, Bieker M, Slotman BJ, Senan S: Volumetric intensity-modulated arc therapy vs conventional IMRT in head-and-neck cancer: a comparative planning and dosimetric study Int
J Radiat Oncol Biol Phys 2009, 74(1):252-259.
doi:10.1186/1748-717X-5-95 Cite this article as: Dobler et al.: Application of volumetric modulated arc therapy (VMAT) in a dual-vendor environment Radiation Oncology
2010 5:95.
Submit your next manuscript to BioMed Central and take full advantage of:
• Convenient online submission
• Thorough peer review
• No space constraints or color figure charges
• Immediate publication on acceptance
• Inclusion in PubMed, CAS, Scopus and Google Scholar
• Research which is freely available for redistribution
Submit your manuscript at www.biomedcentral.com/submit